The invention relates to a sealed antifriction bearing in which the seals at the axial ends of the bearing help convey lubricant into the bearing.
These so-called dirt-protected bearings are used, for example, in oil-lubricated gearing or environments where dirt is generated, as by friction in gearing. Seals are disposed at the axial ends of the annular space between the bearing rings. At least one annular lip of the seal is intended to form a seal at one ring of the bearing, which rotates past that lip.
Various requirements for these bearings appear at least partially contradictory. These requirements include good sealing against dirt, low moment of friction, low breakaway moment and long life.
The first requirement can be satisfied by the sealing lip being pressed with a high pressing force against the application surface of the bearing ring against which it seals. That, however, results in a high moment of friction and rapid wear. Lubrication of the sealing lip or edge, for instance, by the dirtied oil surrounding it, promotes the danger of dirtying of the bearing. To prevent this, several sealing embodiments are provided with means which return the oil outward of the seal. See, for example, Federal Republic of Germany Pat. No. 25 36 374, British Pat. No. 499,480 and Federal Republic of Germany Provisional Pat. No. AS 16 00 458. See also U.S. Pat. No. 4,399,998. Shaft seals are also known in the prior art. See U.S. Pat. Nos. 3,640,542 and 3,586,342.
In this way, the sealing off of the bearing from dirt and oil is improved. But, the breakaway moment and the moment of friction are increased. The conveying of oil out of the bearing, which is sealed off on both sides, produces a vacuum within the bearing which draws the sealing edges or lips against their application surfaces at the rotating bearing rings and thus also increases the moment of friction. The bearings become warmer in operation. When they are allowed to cool down upon stopping operation, there is a further increase in the vacuum and the sealing edges are drawn in even more firmly. This produces a high breakaway moment and a high moment of friction upon restarting.